Research will be on the contols of animal cell division. We now have evidence that animal cells are committed to divide or not divide at a point (R) in the G1 part of their cell cycle. We have further proposed that many malignant cell lines have lost their R-point controls. To test this last idea we intend to investigate R-Point control in various malignant cell lines. We will examine virus-transformed and chemically transformed culture lines, and also spontaneously arising tumor cells, both animal and human. By using mutagens and carcinogens we hope to get mutants useful for these and later studies. We also have proposed that loss of the R-point control makes cells more susceptable to death under adverse conditions. We hope to study the lethal and growth-inhibitory effects of anti-cancer compounds in vitro, to see whether they tp normal cells at the R-point, but not malignant cells (which we expect to stop at random points in their cycle and die). Experiments on the subcellular basis of R-point control will be continued. We are at present looking at poly A synthesis, and at membrane transport changes. Cell divisionof bacteria will continue to be inestigated, as a model system. Roles of membrane proteins are also being investigated.